MONTREAL -- Semen can still contain HIV even if there's no sign of the virus in the plasma, researchers said here.

Action Points

Explain to interested patients that some leading researchers have suggested that effective HIV treatment essentially renders a patient noninfectious.

Note that these studies both found that even when HIV is undetectable in blood, it may still be present and potentially infectious in semen.

These studies were published as abstracts and presented orally at a conference. These data and conclusions should be considered to be preliminary as they have not yet been reviewed and published in a peer-reviewed publication.

MONTREAL, Feb. 10 -- Semen can still contain HIV even if there's no sign of the virus in the plasma, researchers said here.

The finding flies in the face of a much-debated 2008 statement that men with well-controlled HIV and no other sexually transmitted disease are essentially no longer infectious.

Dr. Marcelin presented one of two studies at the 16th Conference on Retroviruses and Opportunistic Infections showing that even when HIV is undetectable in blood, some men shed the virus in semen.

In some cases, the semen can infect cells in vitro, which implies a risk of transmission, said Prameet Sheth, a Ph.D. student at the University of Toronto, who presented the other study.

"To me, this is the next chapter in a book [titled] 'We Can't Treat Our Way Out of this Epidemic,'" said Sharon Hillier, Ph.D., of the University of Pittsburgh, who chaired a press conference at which the research was discussed.

Dr. Hillier said there's no question that treating a group of patients "and driving down their infection" is going to make them less infectious as a group.

"But these data are critically important in showing us -- yet again -- that that alone is not going to be an answer, because there will be some people who continue to shed virus in the face of really effective antiretroviral therapy," she said.

Aside from the Swiss consensus statement, several leading HIV researchers -- including International AIDS Society president Julio Montaner, M.D. of the British Columbia Center of Excellence in HIV/AIDS -- have supported treatment as a way to reduce the rate of transmission. (See: IAC: More HIV Treatment May Reduce Transmission Risk)

The danger of that, Dr. Hillier said, is that some people may assume that a reduction in the risk of transmission is the same as no risk.

"We don't want to give people the notion that their transmission risk is negligible, just because they're on highly active antiretroviral therapy," she said.

The two studies here took different routes to essentially the same message.

Sheth and colleagues performed two studies -- a prospective look at 25 patients starting therapy and a cross-sectional analysis of 13 men on long-term treatment.

In both groups, effective therapy was defined as undetectable HIV in the blood -- fewer than 50 copies of HIV RNA per milliliter of plasma.

The 25 men starting treatment consistently reached that level by week 16 of therapy, Sheth said, but despite that, HIV was detected in semen in 12 of them and at high levels -- more than 5,000 copies per milliliter -- in four.

Among the 13 men with longer viral control -- the median was 126 months -- isolated semen HIV shedding was detected in four, or 31%, he said.

In the French study, Dr. Marcelin and colleagues studied 145 men over a six-year period, during which they provided 264 paired blood and semen samples.

Most of the paired samples were concordant -- 225 samples had undetectable HIV both in blood and semen and nine had HIV in blood and semen.

However, she said, 23 blood samples had detectable HIV although the seminal viral load was undetectable and seven seminal samples had detectable HIV although the blood viral load was undetectable.

Those seven -- about 5% of the total -- corresponded to seven distinct patients, all of whom had had undetectable HIV in blood plasma for at least six months and had no other STD.

The Toronto study was supported by the Canada Research Chair Program, the Ontario HIV Treatment Network, and the Canadian Institutes of Health Research.

The Paris study was supported by the French National Agency for AIDS Research.

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